Metal vapor rectifier



Aug. 9, 1932. E. KERN 1,870,513

METAL VAPOR RECTIFIER Filed June 18, 1928 2 Sheets-Sheet 1 h Fig. 4

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METAL VAPOR RECTIFIER Filed June 18, 1928 2 Sheets-Sheet 2 INVe-NTOP,

Patented Aug. 9, 1932 UNITED STATES PATENT OFFICE ERWIN KERN, OF WETTINGEN, SWITZERLAND, ASSIGNOR TO AKTIENGESELLSCHAFT BROWN, BOVERI AND CIE, OF BADEN, SWITZERLAND METAL VAPOR RECTIFIER or only temporarily during the back ignition through return current relays or differential relays which respond to a return current. In normal working conditions the resistances co-ordinated to the different partial anodes of one phase of a polyphase rectifier are connected up in parallel, so that the resistance which is effective for the normal current is small. When, however, aback ignition takes place at an anode, it will be extinguished by the resistance belonging to the partial anode, the return current being forced to pass through zero.

In spite of this, however, it may occur that after the back ignition has been interrupted the cause of the back ignition will not have been removed, so that a back-ignition current might innnediately occur again. In order to remove this danger, according to the present invention a negative extinguishing voltage is connected up in a known manner by the quick-acting return current relays serving the resistances or by differential relays which become operative selectively in the case of a return current to the grids coordinated to the anodes. In this way the recurrence of a return current is prevented. The present invention therefore relates to a method of suppressing back ignitions in metal vapor rectifiers, in which in a known manner the return current is brought artificially to zero by additional ohmic resistances which are connected up in the back ignition circuit by relays either permanently or during the back-ignition and in which the grids co-ordinated to the anodes are charged negatively with respect to the back igniting anode by the coming into operation of the return current relay or of the dillerential relay which operates selectively in the case of a return current flowing.

In the accompanying drawings two constructional examples of the invention are shown diagrammatically, Fig. 1 being a longitudinal section showing the arrangement with resistances which are connected up temporarily in the anode circuit, on a back-ignition occurring, and Flg. 2 being a partial sectionshowing the arrangement as applied to a rectifier having a resistance permanently connected up in the anode circuit. Figure 3 is a detail diagrammatic drawing of the differen'tial relay employed.

In the example shown in Fig. 1 of the drawing 5 is the transformer feeding the rectifier, a the rectifier with the anodes b and the cathode c, and cl are the controlling grids or sleeves belonging to the anodes, which are fed from the battery g through the loading resistance It. The sleeves are insulated with respect to the anodes. The return current relays are marked 6. f is the ohmic resistance in the anode circuit, which periodically reduces the return current to the value zero.' In normal working conditions this resistance is short-circuited by the armature i of the return current. relay 0, so that the current will flow to the anode without passing through the resistance, while the battery 9 for the controlling grid is disconnected. On a back-ignition occurring, however, the return current relay 6 will become operative, the resistance f is connected up and the battery 9 is connected to the grid cl.

In the example shown in Fig. 2 in place of the resistance f which is connected up temporarily by the relay 6 on a back-ignition occurring, a subdivided anode is provided with resistances f which are permanently connected up. In this case the return current relay 6 thus only controls the battery 9 for the grid control. For the rest the arrangement and manner of operation is the same as in Fig. 1, i. e., on a back-ignition occurring, the I return current is periodically brought by the resistances to the value zero, the grid control battery 9 which charges the grid negatively with respect to the back-igniting anode being at the same time connected up by the return current relay 0.

This relay is constructed and operates as follows, having reference to Figure 8 of the drawings :r represents the pivot of the polarized armature 0 of the relay 6, which bridges over the contacts 39 or g; n is an iron core, which has abutments m on which the armature normally rests. 70 indicates an auxilary source of direct current for polarizing the armature o. The anode lead is passed through the iron core n of the relay. The auxiliary source of current polarizes the armature in such'a manner that in normal operation it rests against the abutments m and the contact member 2' secured to the armature 0 closes the contacts p. If, now, owing to a back-ignition the direction ofcurrent 1n the anode conductor is reversed, the polarity of p the magnet field of the iron core n also changes, the armature 0 rotates in a clockwise direction and closes the contacts 9 and efi'ects the necessary switching.

, What I claim is: Y

1. In a metal vapor rectifier, means for suppressing back-ignition including a difl'erential selective relay to operate in the case of a return current connected to the backignition circuit, an additional ohmic resistance brought into use by the relay'and connected in the back-ignition circuit, a grid interposed between each anode and the oathode, and means to charge the grid negatively on the operation of the said relay.

2. In a metal vapor rectifier, means for suppressing back ignition including a reverse current relay, an additional ohmic resistance brought into use by the relay on a reverse current flowing connected in the back ignition circuit, a grid interposed between each anode and the cathode, and means to charge the grid negatively on the operation of the said relay.

In testimony whereof I have signed my name to this specification.

ERWIN KERN. 

